title: TDP-43 Phosphorylation by casein kinase Iε promotes oligomerization and enhances toxicity in vivo.
abstract: Dominant mutations in transactive response DNA-binding protein-43 (TDP-43) cause amyotrophic lateral sclerosis. TDP-43 inclusions occur in neurons, glia and muscle in this disease and in sporadic and inherited forms of frontotemporal lobar degeneration. Cytoplasmic localization, cleavage, aggregation and phosphorylation of TDP-43 at the Ser409/410 epitope have been associated with disease pathogenesis. TDP-43 aggregation is not a common feature of mouse models of TDP-43 proteinopathy, and TDP-43 is generally not thought to acquire an amyloid conformation or form fibrils. A number of putative TDP-43 kinases have been identified, but whether any of these functions to regulate TDP-43 phosphorylation or toxicity in vivo is not known. Here, we demonstrate that human TDP-43(Q331K) undergoes cytoplasmic localization and aggregates when misexpressed in Drosophila when compared with wild-type and M337V forms. Coexpression of Q331K with doubletime (DBT), the fly homolog of casein kinase Iε (CKIε), enhances toxicity. There is at best modest basal phosphorylation of misexpressed human TDP-43 in Drosophila, but coexpression with DBT increases Ser409/410 phosphorylation of all TDP-43 isoforms tested. Phosphorylation of TDP-43 in the fly is specific for DBT, as it is not observed using the validated tau kinases GSK-3β, PAR-1/MARK2 or CDK5. Coexpression of DBT with TDP-43(Q331K) enhances the formation of high-molecular weight oligomeric species coincident with enhanced toxicity, and treatment of recombinant oligomeric TDP-43 with rat CKI strongly enhances its toxicity in mammalian cell culture. These data identify CKIε as a potent TDP-43 kinase in vivo and implicate oligomeric species as the toxic entities in TDP-43 proteinopathies.
authors.affiliation: Department of Neuroscience and Cell Biology.
authors.forename: Darshana K
authors.initials: DK
authors.lastname: Choksi
authors.forename: Bidisha
authors.initials: B
authors.lastname: Roy
authors.forename: Shreyasi
authors.initials: S
authors.lastname: Chatterjee
authors.forename: Tanzeen
authors.initials: T
authors.lastname: Yusuff
authors.forename: Mathieu F
authors.initials: MF
authors.lastname: Bakhoum
authors.forename: Urmi
authors.initials: U
authors.lastname: Sengupta
authors.forename: Suren
authors.initials: S
authors.lastname: Ambegaokar
authors.forename: Rakez
authors.initials: R
authors.lastname: Kayed
authors.forename: George R
authors.initials: GR
authors.lastname: Jackson
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000201:enzymology; D000818:Animals; D030801:Animals, Genetically Modified; D048149:Casein Kinase 1 epsilon / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster; D006801:Humans; D060227:Imaginal Discs / Q000378:metabolism; D020125:Mutation, Missense; D010766:Phosphorylation; D055503:Protein Multimerization; D011499:Protein Processing, Post-Translational; D051381:Rats
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C113519:dco protein, Drosophila; D048149:Casein Kinase 1 epsilon